Graphene is a two-dimensional, honeycomb lattice arrangement with unique physical properties. To overcome the disadvantage of small-scale production of graphene using mechanical exfoliation of highly orientated polymeric graphite (HOPG), chemical vapor deposition (CVD) of large-area single-layer graphene on metal films has been explored from various aspects. Despite significant progress, CVD graphene is usually a polycrystalline film made of small grains. The grain boundaries have been found to impede both transport and mechanical properties, and growth of large-grain, single-crystalline graphene for various applications has been explored. One method involves using a copper enclosure to grow large graphene single crystals. This process, however, depends on how the copper enclosure is manually made, and the copper enclosure does not allow probing the gas environment inside.